Magnetic amplifier and self-modulator



Oct. 11, 1927. 5,302

J. SLEPIAN MAGNETIC AMPLIFIER AND SELF MODULATOR Fig.1

Original Filed April 21. 1921 onnnnn'n AudioJoume Fig.9.

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' ATTORNEY relatively large or small amounts Patented Oct. 11, 1927.

UNITED STATES PATENT OFFICE.

JOSEPH SLEPIAN, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

MAGNETIC AMPLIFIER AND SELF-MODULATOR.

Application filed Apri1 21, 1921, Serial No. 463,209. Renewed February 14, 1927.

My invention relates to wireless telegraphy and particularly to an.electr 1cal system which may be employed either to amplify or to modulate the variable currents employed in wireless and 1n telephone systems.

One object of my invention is to provide a magnetic amplifier system wherein of energy may be easily and efliciently amplified.

Anotherlobject of my invention is to provide simple and efficient means for modulating at an audible frequency, the energy radiated from high-power continuous-wave wireless transmission systems.

A still further object of my invention is to provide a wireless transmission system which embodies means necessary to render the system effectiveas a self-modulator to admit of the radiation of successive groups of electromagnetic wave trains similar to those produced by spark transmitters.

In the present state of the art, it is customary to amplify the variable currents employed in wireless telephony and tele-- graphy through the utilization of thermionic devices and magnetic relays. One disadvantage of such amplifying devices, however, is the limitation i'n the power of input and output thereof.

Furthermore, in the art ofsignaling, it has been customary, in stations radiating sustained waves, to communicate with receiving stations unable to receive such waves by employing a special spark transmitter. According to my invention, I provide an electrical system which may, with slight modifications in the design thereof, be employed either as an amplifier, or as a selfmodulator in wireless transmission systems. Briefly speaking, my invention comprises a circuit having radio-frequency currents therein, a second quency currents therein, a magnetizable member inductively associated with said circuits, and means included in the firstnamed circuit for causing the modulations of the radio-frequency currents to lag be hind the modulating audio-frequency currents.

I have found that, if, the losses in the cir- "cuit having the audio-frequency currents therein aresufiiciently small, the efl ect of the lag between .the currents just mentioned circuit having audio-fre included, respectively,

is to cause power to be supplied from the quency currents without additional audio input. Thus my system may become a selfmodulator.

I have further found that, if my system is so adjusted that it is at the point of sustaining currents in the audio-frequency circuit, small changes in the value of the audio input effect relatively large changes in the .value of the radio-frequency currents.

Other objects as well as details of construction, whereby my invention may be carried out, will be apparent from the following description taken in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of circuits and apparatus embodyingmy invention;

Fig. 2 is a View similar to Fig. 1, but showing my invention effective as a self- .modulator in a wireless transmission system.

Figs. 3, 4, 5, 6 and 7 are curves, assuming the radio-frequency circuits non-resonant, which show, respectively, the impressed audio-frequency currents, the variations in permeability of the magnetizable member associated with the radio-frequency circuit and the audio-frequency circuit, the modulated radio-frequency currents, the mean flux change in the magnetizable memher due to the radio-frequency currents, and the modulated audio-frequency electro-motive force. I

Fig. 8 is a curve showing the shift in phase that is efiected between the audiofrequency currents and the modulated radiofrequency currents upon the insertion of capacitance and inductance in the radiofrequency circuit.

' Fig. 9 is a diagrammatic view of circuits and apparatus embodying my invention in a modified form.

Referring to Fig. 1, a radio-frequency circuit 1 is operatively connected to a local source of radio-frequency currents 2 through coupling coils 3 and 4, and to an audio-circuit 5 through a coupling transformer 6. The transformer 6 has of magnetizing w'mdings 7 and 8 which are in the radio-frequency circuit 1 and the audiofrequency circuit 5.

The high-frequency source 2 is shown, for

wound thereon a pair the purpose of illustration, as an arc generradio-choke coil 14, and a condenser for tuning the audio-frequency circuit 5 to resonance with the audio-frequency curents.

The radio-frequency circuit 1 comprises the coupling coil 3, the magnetizing winding 7, an inductance coil 16 and a, condenser 17 for tuning the circuit substantially to resonance with the source of energy 2, and the rectifier circuits 18 and 19 which are connected in shunt to each other and in series relation in circuit 1. The rectifier circuits 18 and 19 include, respectively, indicating devices 23 and 24 and rectifiers 21 and 22 which are connected in opposition. The indicating devices 23 and 24 may be shunted also by the coupling coils 13 and 12, which are connected in opposition as shown.

The degree of saturation of the transform.- er 6 may be controlled by means of a circuit 25 which comprises a magnetizing winding 26, a radio-choke coil 26', an adjustable resistor 27 and a direct-current source of energy 28. In operation, the flux density of the magnetizable core of the transformer 6 may thus be adjusted to the knee of its magnetlzation curve, in .order to obtain maximum eificiency. I

Referring to Fig.2, the system shown differs from that of Fig. 1 in that the condenser 17 has been replaced by an antenna 29. In addition, the arc 9 has been directly included in. the radio-frequency circuit 1. A further distinction is that the audio-frequency circuit 5 has been caused to include the inductance coil 14, the condenser 15 and the magnetizing winding 8, energy for the circuit 5 being derived solely from the radio-frequency circuit 1.

The curve diagrams shown in Figs. 3 to 7, inclusive, explain the fact that, if the radiofrequency circuit 1 is non-resonant to the source of energy 2, as effected by the removal of the reactors 16 and 17 therefrom, the modulation of the currents therein by the audio-frequency currents may be effected with just suflicient power input in the audiofrequency circuit to supply the energy losses in the magnetic device 6.

' Fig. 3 is a curve diagram showing the wave form of the currents in-the audio-frequency circuit 5.

Fig. 4 is a curve diagram showing the changes in the permeability of the core of the transformer 6 that are caused by the impressed audio-frequency currents.

Fig. 5 is a curve diagram showing the effect of the varying permeability of the transformer core upon the radio-frequency currents in circuit 1. As can be readily seen, the radio-frequency currents are modulated at a frequency corresponding to that of the audio-frequency circuit 5. In Fig. 5, curve 31, represents the radio-frequency oscillations, and curve 30 represents the audio-frequency modulation thereof.

In view of the fact that the core of the transformer 6 is saturated, or partially saturated, by the unidirectional exciting coil 26,

the positive half-wave of the radio-frequency current will produce very little change in the flux, whereas the negative half-cycle will produce a relatively largechange. The resulting flux changes are indicated in Fig. 6 as well as a smooth curve showing the mean-flux modulations.

Fig. 7 is a curve diagram showing the audio-frequency voltage produced in coil 8 by reason of the flux modulations shown in Fig. 6.

By comparing Figs. 3 and 7, it will be seen that the current in the audio-frequency circuit and the voltage produced therein by the modulations of the current in the radiofrequenc circuit are in quadrature, and hence neither circuit exchanges power with the other. In other words, the audio-frequency source effectsthe modulation of the radio-frequency current with just sufiicient.

power to supply the energy losses in the transformer 6.

The reason for the lag shown in Fig. 8, which is produced by the tuning of the series-resonant reactance devices 16 and 17 to the frequency of the energy source 2, will probably be best understood by a consideration of the energy stored by the devices. I

If an oscillatory electromotive force of constant amplitude is suddenly impressed upon an oscillatory circuit containing the seriesresonant devices 16 and 17, the current will not immediately reach a steady value, since the energy stored in the resonant devices must be supplied from the source, but the amplitude of the oscillations will gradually increase for a number of cycles, dependent upon the ratio of the stored energy to the resistance load, as is well known. Similarly, if the oscillatory electromotive force is decreased in amplitude, or withdrawn :11- together, the excess energy stored in such reactance device will cause the corresponding modulation of the current tobe postponed to a time which may be a number of cycles later.

The result of such lag in the present device is that the audio-frequency electromoquency circuit 5 by the modulated radiofrequency current in circuit 1 has a component in phase with the audio-frequency current flow in circuit 5, as well as a component in quadrature therewith. Energy is thus'supplied to the audio-frequency circuit 5 from the radio-frequency circuit 1, tending to reduce the necessary audio-frequency power input.

By sufliciently reducing the losses in the audio-frequency circuit, enough power may be supplied thereto from the radio-frequency circuit to maintain currents therein without additional audio input. The system then becomes a self-modulator. In Fig. 2 T have shown such an arrangement wherein, upon the energization of the are 9, the sustained currents traversing the circuit 1 are modulated at an audible frequency to cause the radiation of successive groups of electromagnetic energy. 1

When my system is employed as an amplifier, it is most efiicient when the resonance of the reactance devices 16, 17 and the unidirectional execitation of the coil 26 are so chosen that the radio-frequency circuit almost sustains the oscillations'in the audiofrequency circuit 5. Further amplification may be obtained by means of the feed-back coils 12 and 13 and the coupling coil 11, said coils feeding back energy in accordance with the audio-frequency modulations of the currents in the radio-frequency circuit.

Referring to Fig. l and assuming radiofrequency currents supplied to the radiofrequency circuit 1 by means of the SOllICe of radio-frequency energy 2, the eflect of impressing currents of an audible frequency upon circuit 5 is to effect the modulation of the radio-frequency currents in circuit 1 at frequencies corresponding to those in the audio-frequency circuit 5, all as hereinbez fore described. The effect of the rectifiers 21 and 22 is to render audible in the indicating devices 23 and 24, the note corresponding to that of the audio-frequency component of the modulated currents.

Referring to Fig. 2, upon the adjustment of the flux density of the transformer 6 to the knee of its saturation curve, and upon the energization of the are 9 successive groups of electromagnetic energy of an audible group fr uency are radiated.

In Fig. 9, I ave shown a modified arrangement 'which has proved desirable in practice. The high-frequency current is' transmitted, through coupling coils 4, 3, to the primaries of two magnetic amplifiers 33, 34 similar to the transformer 6 of Figs. 1 and 2. The direct-current source 28 is included in circuit withthe 'rimary.windings, thus dispensing with the third winding 26. No ,attempt is made to tune the radio-frequency circuit in which said primary windings are included. A

satauration of the other is increased, thus unbalancing the secondary high-frequency electromotive forces. A pair of telephone receivers 23, 24 connected across the terminals of the secondary windings, through oppositely acting rectifiers 21, 22, as in Fig. I, serve to detect the modulated highfrequency currents. The circuit including the telephones may be tuned to the highfrequency currents as by the inclusion of the series-resonant device 16', 17 in-order to increase the audio-frequency power drawn from the high-frequency source, ashereinabove explained.

The self-modulating charactetristic of my system is of particular importance in marine work in that it eliminates the-spark transmitting apparatus which has been generally used in conjunction with continuous-wave systems when desiring to communicate with receiving systems responsive only to energy radiated by spark transmitters.

Another advantage of my invention resides in the provision of a magnetic amplifying system wherein large amounts of pogver may be simply and efliciently ampli- It will be seen, therefore, that my invention provides a simple and inexpensive system which, with slight modifications, may be employed as an amplifier or as a modulator.

While I have shown nly three embodiments of my invention, it is capable of various other changes and modifications in the design and arrangement of the system, without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed thereon as are set forth in the appended claims.

I claim as my invention:

1. The process of amplifying audio-frequency currents which consists in modulating an ultra-audio-frequency current by means of said audio-frequency currents, feeding back energy from said ultra-audiofrequency currents to said audio-frequency currents, and in .detecting said modulated ultra-audio-frequency current.

2. The combination with a circuit having ultra-audio-frequency currents therein, of a circuit having audio-frequency currents therein, means for varying the impedance of said ultra-audio-frequency circuit in accordance with currents in said audio-frequency circuit, and auxiliary means for controlling the phase of the audio-frequency changes in the ultra-audio-frequency circuit and thereby causing a transfer of audiofrequency power from said ultra-audiofrequency circuit to said audio-frequency circuit.

3. The combination with a circuit having ultra-audio-frequency currents therein, of a circuit having audio-frequency currents therein, means for varying the impedance of said ultra-audio-frequencycircuit in accordance with currents in said audio-frequency circuit, means 'for rectifying said ultra-audio-frequency currents, and means for causing a transfer of audio-frequency power from said ultra-audio-frequency circuit through said impedance-varying means to said audio-frequency circuit.

4. In combination, a primary circuit, a source of ultra-audio-frequency current feeding said primary circuit, a transformer core providing a one-way path for the flux, said primary circuit including a primary winding on said core, a secondary circuit including means for preventing the flow of ultraaudio-frequency currents therein and also including a secondary winding on said core, and means for keeping said core at approximately that degree of saturation at which the change of permeability with change in current is a maximum, whereby changes in said'audio-frequency currents will produce large changes in the inductance of said primary winding and the energy imparted to said secondary circuit from said trans former will be audio-frequency energy.

5. The combination with a source of ultraaudio-frequency electromotive force, of an lron-core transformer having its primary w nding connected to said source, a circuit connected to the secondary winding of'said transformer, said circuit being tuned to an audible frequency, unidirectional exciting means for said transformer, whereby the reactance of said primary winding is varied in accordance with the currents in said audio-frequency circuit, and means for causing the modulations of the currents in said ultra-audio-frequency circuit to lag behind the variations in the reactance of said primary winding.

6. The combination with a source of ultraaudio-frequency' electromotive force, of an iron-core transformer having its primary winding connected to said source, a circuit connected to the secondary winding of said transformer, said "circuit being tuned to an audible frequency, unidirectional exciting means for said transformer, whereby the reactanceof said primary winding is varied in accordance with the currents in said audio-frequency circuit, and a series-resonant reactance device tuned to the frequency of said source for causing the modulations device in series with each of said receivers,

'said rectifying devices being oppositely connected.

8. In an electrical system, a circuit having audio-frequency currents therein, a circuit having ultra-audio-frequency currents therein, means for causing said audio-frequency currents to modulate said ultra-audio-fre quency currents, and means whereby power may be supplied to said first-named circuit from said second-named circuit through said first-named means. A

9. In an electrical system, a circuit having audio-frequency currents therein, a circuit having ultra-audio-frequency currents therein, means for causing the modulation of said ultra-audio-frequency currents by said audiofrequency currents, and means whereby the modulation of said radio-frequency currents is caused to lag behind said modu lating audio-frequency currents to admit of a transfer of power from said second-named circuit to said first-named circuit through said first-named means,

10. In an electrical system, a circuit having audio-frequency currents therein, a circuit having ultra-audio-frequency currents therein, means associated with both of said circuits for causing the modulation of said ultra-audio-frequency currents by said audio-frequency currents, one of said circuits including capacitance and inductance devices resonant to said ultra-audio-frequency currents, whereby the modulation of said ultra-audio-frequency currents 1s caused to lag behind said modulating audiofrequency currents to admit of a transfer of energy from said second-named circuit to said first-named circuit.

11. In a magnetic amplifier, a circuit having sustained ultra-audio-frequen'cy currents therein and a magnetizing winding, a circuit having audio-frequency currents therein and a magnetizable winding, a magnetizable member associated with said magnetizing windings, whereby said audio-frequency currents ma ductanoe whereby the modulation of said ultra-audio-frequency currents 'is caused. to lag behind said modulating audio-frequency currents, said magnetizable member being so related tosaid windings that said lagwill be caused to modulate said .ultra-audiorequency currents, said fir stnamed circuit'including capacitance and 1n-' occasion a transfer of energy from said firstnamed circuit to said second-named circuit through said magnetizable member.

12. In a magnetic amplifier, a circuit carrying audio-frequency currents and including a magnetizing winding and a coupling coil, a circuit carrying ultra-audiofrequency currents and including a magnetizing winding, a pair of rectifiers connected in parrallel opposition and indicating devices associated therewith, and a magnetizable member associated with said first and second-named circuits whereby said audiofrequency currents may be caused to modulate said ultra-audio-frequency currents.

13. In a magnetic amplifier, a circuit hav ing audio-frequency currents therein and a magnetizingwinding, a circuit having u1traaudio-frequency currents therein and including a magnetizing Winding, a pair of rectifier circuits connected in shunt to each other, each rectifier circuit containing a rectifier and an indicating device, said rectifiers being connected oppositely, and a magnetizable member associated with said magnetizing windings, whereby said audiofrequency currents may be caused to modulate said ultra-audio-frequency currents.

14:. In combination, a source of radio-frequency currents, a source of audio-frequency currents, a circuit adapted to carry said radio-frequency currents, a circuit adapted to carry said audio-frequency currents, a magnetizable member inductively associated with both of said circuits, and means Whereby the modulation of said radio-frequency currents occasioned by said audio-frequency currents is caused to lag behind the modulating audio-frequency currents.

In testimony whereof, I have hereunto subscribed my name this 14th day of April, 1921.

JOSEPH SLEPIAN. 

